Mouth rinse or mouthwash compositions have been used by people for many years for the prevention of bad breath and for the elimination of bacteria and other oral microorganisms that are responsible not only for bad breath but also tooth decay, plaque and gum diseases such as gingivitis and periodontitis. To this end, antiseptic mouthwashes in the past have been designed to clean the oral cavity, provide fresh breath and kill these pathogenic microbes.
Leading antiseptic mouth rinses have traditionally contained alcohol (i.e., ethanol) at fairly high levels, ranging from approximately 20% up to about 30% by volume, based on the total mouthwash volume (hereinafter referred to as “% v/v”). Alcohol is used both as a vehicle and as a solvent in which the active ingredients, and additives such as astringents, fluorides, color additives, flavor oils, and the like, can be dissolved and then dispersed into solution. Alcohol also provides a preservative role for the mouth rinse during storage and use, and enhances the flavor oil organoleptic cues.
However, the use of high levels of alcohol may sometimes be found unacceptable by some mouthwash users. Senior citizens have also complained about problems related to gargling with such mouth rinses, and chronic exposure has been found to result in a feeling of gum “burn” resulting from the high concentrations of alcohol. It has also been reported that alcoholic mouth rinses can result in an unpleasant “dry mouth” sensation.
On the other hand, reducing the levels of alcohol in these mouth rinse compositions can have significant disadvantages. It has been found that lower alcohol concentrations result not only in a loss in the solubility of the actives and other ingredients in the composition, but also in a noticeable decrease in the ability of the composition to kill the oral microorganisms responsible for bad breath, plaque and gum disease. This loss in antimicrobial activity is not only due to the reduction of alcohol as a vehicle, but also to the reduced bioavailability of the solubilized actives.
Thymol, for example, is a well known antiseptic compound, also known as an essential oil, which is utilized for its antimicrobial activity in a variety of mouthwash or mouth rinse preparations. In particular, thymol can be utilized in oral hygiene compositions such as mouth rinses in sufficient quantities to provide desired beneficial therapeutic effects. Mouthwashes with thymol are well-known, and have been used by millions of people for over one hundred years. They have been proven effective in killing microbes in the oral cavity that are responsible for plaque, gingivitis and bad breath. Thymol, together with other essential oils such as methyl salicylate, menthol and eucalyptol, comprise the active component in some antiseptic mouth rinses. These oils achieve good efficacy although present in small amounts. Without being restricted to any specific theory, it is now believed that the efficacy and taste of antiseptic mouth rinses may be due to the improved dispersion or dissolution of the oils and bioavailability after such dispersion or dissolution of these four active ingredients.
The above described dispersion or dissolution is also important from an aesthetic point of view since a clear mouth rinse solutions are certainly more preferred by consumers than cloudy, turbid or otherwise heterogeneous ones. Obviously then, there is a substantial need for the development of a reduced and/or no alcohol mouth rinses which provide improved dispersion or dissolution of the essential oils yet maintain the bioavailability of the essential oils for preventing bad breath, killing oral microbes and reducing or eliminating plaque.